Effects of gluten-free diet intervention in the treatment of Hashimoto's thyroiditis in non-celiac disease: A systematic review protocol.

Objective. Hashimoto's thyroiditis (HT) is a prevalent condition characterized by increased thyroid antibody titers (TAT) in non-celiac disease. The emergence of a gluten-free diet (GFD) as a potential treatment for reducing TAT and HT symptoms is a promising development. However, the potential benefits of gluten withdrawal in HT are not fully understood and the overall evidence is inconclusive. The aim of this review article is to present a systematic protocol for evaluating the effects of a GFD intervention in the treatment of HT in non-celiac disease. Methods. Randomized controlled trials in adults and older people with HT and non-celiac disease following the GFD intervention compared to any gluten dietary and no dietary interventions or placebo (as long as it contains gluten) will be included. We will use Cochrane Central, Medline, Lilacs, Embase, Scopus, and Web of Science for the search. Free triiodothyronine (fT3), free thyroxine (fT4), thyroid stimulating hormone (TSH), TAT - anti-thyroid peroxidase (TPO) and anti-thyroglobulin (Tg), C-reactive protein (CRP), vitamin D, adverse effects, body weight, body mass index (BMI), diet adherence and health-related quality of life will be used as the outcomes. We will present the results in a narrative format and if possible, we will conduct a meta-analysis using a random effects model. The certainty of the evidence using the Grading of Recommendations Assessment Development and Evaluation (GRADE) will be assessed. Conclusion. We will disseminate the results through peer-reviewed publications, social networks, and educational talks. The systematic review will provide valuable information on the effects of the GFD in the treatment of HT in non-celiac disease verifying its impact mainly on TAT.